Sunday, July 27, 2014

New paper finds 'high correlation between solar activity and Earth's temperature over centuries'

A new paper published in the Chinese Science Bulletin finds "high correlation between solar activity and the Earth's averaged surface temperature over centuries."
The paper is written in Chinese, but has an English abstract [below] and a press release which states,

"results demonstrate that solar activity and the Earth’s temperature have significant resonance cycles, and the Earth’s temperature has periodic variations similar to those of the solar activity (Figure 1).

The study also implies that the “modern maximum” of solar activity agrees well with the global warming of the Earth during the past century. A significant correlation between them can be found (Figure 2). Especially, the correlation between the solar activity and the ocean temperature is higher than the correlation between the solar activity and the land temperature. These results, as pointed out by a peer reviewer, “provide a possible explanation for the global warming”.

The global wavelet coherence between Sunspot number (a), Total Solar Irradiance (b) and the anomalies of the Earth's averaged surface temperature. The resonant periodicities of 21.3-year (21.5-year), 52.3-year (61.6-year), and... Click here for more information.

A recent study demonstrates the existence of significant resonance cycles and high correlations between solar activity and the Earth's averaged surface temperature over centuries. This provides a new clue to reveal the phenomenon of global warming in recent years.

Their work, entitled "Periodicities of solar activity and the surface temperature variation of the Earth and their correlations" was published in CHINESE SCIENCE BULLETIN (In Chinese) 2014 No.14 with the co-corresponding authors of Dr. Zhao Xinhua and Dr. Feng Xueshang from State key laboratory of space weather, CSSAR/NSSC, Chinese Academy of Sciences. It adopts the wavelet analysis technique and cross correlation method to investigate the periodicities of solar activity and the Earth's temperature as well as their correlations during the past centuries.

Global warming is one of the hottest and most debatable issues at present. The Intergovernmental Panel on Climate Change (IPCC) claimed that the release of the anthropogenic greenhouse gases contributed to 90% or even higher of the observed increase in the global average temperature in the past 50 years. However, the debate on the causes of the global warming never stops. Research shows that the current warming does not exceed the natural fluctuations of climate. The climate models of IPCC seem to underestimate the impact of natural factors on the climate change, while overstate that of human activities. Solar activity is an important ingredient of natural driving forces of climate. Therefore, it is valuable to investigate the influence of solar variability on the Earth's climate change on long time scales.

This innovative study combines the measured data with those reconstructed to disclose the periodicities of solar activity during centuries and their correlations with the Earth's temperature. The obtained results demonstrate that solar activity and the Earth's temperature have significant resonance cycles, and the Earth's temperature has periodic variations similar to those of solar activity (Figure 1).

This study also implies that the "modern maximum" of solar activity agrees well with the recent global warming of the Earth. A significant correlation between them can be found (Figure 2).

As pointed out by a peer reviewer, "this work provides a possible explanation for the global warming".

Global warming, namely the unequivocal and continuing rise in Earth’s climate, is one of the hottest and most debatable issue at the present time. As a scientific intergovernmental and international body under the auspices of the United Nations (UN), the intergovernmental Panel on Climate Change (IPCC) once claimed that the release of the anthropogenic greenhouse gases contributed to as much as 90% or even higher of the observed increase in the global average temperature in the past 50 years. However, worldwide scientists are still skeptical and debate on the possible explanation of the global warming never ends. Research shows that the IPCC’s model tends to underestimate the impact of natural factors on the climate change, while overestimate that of the human activities.

As a matter of fact, solar activity is an important ingredient of natural driving forces of climate. A recent study done by space physicists at the State Key Laboratory of Space Weather, the National Space Science Center (NSSC) have demonstrated the high correlations between solar activity and the Earth’s averaged surface temperature during centuries. The result will to a large extend provide a new clue to reveal the cause of global warming in recent years.

Supported by NSSC’s “Five Key Cultivation Directions” Fund, Dr. ZHAO Xinhua and Dr. FENG Xueshang combined the measured data with those reconstructed to disclose the periodicities of solar activity during centuries and their correlations with the Earth’s temperature based on the wavelet analysis technique and cross correlation method. Their results demonstrate that solar activity and the Earth’s temperature have significant resonance cycles, and the Earth’s temperature has periodic variations similar to those of the solar activity (Figure 1). The study also implies that the “modern maximum” of solar activity agrees well with the global warming of the Earth during the past century. A significant correlation between them can be found (Figure 2). Especially, the correlation between the solar activity and the ocean temperature is higher than the correlation between the solar activity and the land temperature. These results, as pointed out by a peer reviewer, “provide a possible explanation for the global warming”.

Figure 1: The global wavelet coherence between Sunspot number (a), Total Solar Irradiance (b) and the anomalies of the Earth’s averaged surface temperature. The resonant periodicities of 21.3-year (21.5-year), 52.3-year (61.6-year), and 81.6-year are close to the 22-year, 50-year, and 100-year cycles of solar activity. (Image by NSSC) Figure 2: Comparisons between the 11-year running averaged Total Solar Irradiance (TSI) and the temperature (T) anomalies of the Earth (global, land, ocean). (Image by NSSC)

Periodicities of solar activity and the surface temperature variation of the Earth and their correlations

Based on the well-calibrated systematiCmeasurements of sunspot numbers, the reconstructed data of the total solar irradiance (TSI), and the observed anomalies of the Earth’s averaged surface temperature (global, ocean, land), this paper investigates the periodicities of both solar activity and the Earth’s temperature variation as well as their correlations on the time scale of centuries using the wavelet and cross correlation analysis techniques. The main results are as follows. (1) Solar activities (including sunspot number and TSI) have four major periodic components higher than the 95% significance level of white noise during the period of interest, i.e. 11-year period, 50-year period, 100-year period, and 200-year period. The global temperature anomalies of the Earth have only one major periodic component of 64.3-year period, which is close to the 50-year cycle of solar activity. (2) Significant resonant periodicities between solar activity and the Earth’s temperature are focused on the 22- and 50-year period. (3) Correlations between solar activity and the surface temperature of the Earth on the long time scales are higher than those on the short time scales. As far as the sunspot number is concerned, its correlation coefficients to the Earth temperature are 0.31-0.35 on the yearly scale, 0.58-0.70 on the 11-year running mean scale, and 0.64-0.78 on the 22-year running mean scale. TSI has stronger correlations to the Earth temperature than sunspot number. (4) During the past 100 years, solar activities display a clear increasing tendency that corresponds to the global warming of the Earth (including land and ocean) very well. Particularly, the ocean temperature has a slightly higher correlation to solar activity than the land temperature. All these demonstrate that solar activity has a non-negligible forcing on the temperature change of the Earth on the time scale of centuries.

4 comments:

There does not seem to be anything new here except perhaps the values of the periodicities and correlation coefficients.

As to the estimates of the periodicities, 140 years do not appear sufficient to reveal with confidence periods of 100 and 200 years and barely enough to reveal the 50 year period.

The correlation estimates look reasonable, but we ought to be aware by now that time-series can produce high correlation where there is none at all. Is correlation valid for sunspot and temperature, neither of which can be demonstrated to be normally distributed?

Econometricians use cointegration instead of correlation to avoid spurious correlation.

The paper does provide support for the theories of Svensmark and his group. I therefore believe the authors of this paper have come to the right answer using analysis that is not appropriate for the data.

I wish more climate researchers would team up with econometricians to use polynomial cointegration, which is appropriate for time-series data.

This is addressed by an econometric technique called polynomial cointegration analysis. An Israeli group carried out such an analysis of the inputs (GHG, temperature and solar irradiance data) and concluded,

"We have shown that anthropogenic forcings do not polynomially cointegrate with global temperature and solar irradiance. Therefore, data for 1880–2007 do not support the anthropogenic interpretation of global warming during this period."